Bordetella pertussis is the causative agent of whooping cough. A highly effective inactivated whole cell vaccine has been available since the 1940s but concern over its safety, due to the presence of toxic cellular components, has limited its uptake [1]. Acellular pertussis vaccines(Pa) comprising a small number of defined B. pertussis antigens have therefore been produced, and have been approved for use in humans [2].
Pertussis vaccines are usually administered intramuscularly to children in the form of atrivalent DTP combination (diphtheria, tetanus, pertussis) on alum adjuvant. Intramuscular vaccination is not, however, the ideal route of administration. Mucosal vaccines (oral, intranasal etc.) are preferred for two reasons [3]. Firstly, they are easier to administer on a large scale, avoiding the need for specialized equipment and the problems associated with needles. Secondly, they stimulate mucosal immunity, mediated by secretory IgA. As most pathogens enter the body across mucous membranes, mucosal immunity is desirable.
Attempts to make acellular mucosal pertussis vaccines have been described [e.g. 4,5,6,7,8,9], but the levels of protection reported were either not compared with conventional vaccine, or did not approach that observed the alum-adjuvanted antigens given parenterally.
There is therefore a need for an effective mucosal DTP combination vaccine.